Full-load hours

Full-load hours are a way of measuring energy that power plants create. They are used to show how many hours a plant would take to make a certain amount of energy if the plant is operating at full capacity.

Whereas capacity factor is an indication of capacity utilization as a percentage, one also speaks of “full-load hours,” an especially useful term for dispatchable generators, which can be switched on and off – such as biomass, coal, and natural gas.

There are 8,760 hours in a normal year. The number of full-load hours can be used, say, as an indication of how many hours a particular generator needs to run each year to be profitable. For instance, a particular power plant may need 4,000 full-load hours of operation to be profitable, equivalent to a capacity factor of 4,000 / 8,760 = 45.7 percent. If it runs at 50 percent capacity, it would need to run for 8,000 actual hours to achieve 4,000 full-load hours.